Anti-cancer drug KP1019 induces Hog1 phosphorylation and protein ubiquitylation in Saccharomyces cerevisiae

Ruthenium-based anti-cancer drugs have attracted increasing interest in the last 20 years. KP1019 is one of the ruthenium-containing compounds that has demonstrated anti-tumor activity against various cancers, and has been tested in several clinical trials. Despite its success, the mode of action of KP1019 is not well described. In the present study, we have used budding yeast Saccharomyces cerevisiae to elucidate the action of KP1019. We have found that KP1019 causes dose-dependent cell arrest in the S-phase of cell cycle. Furthermore, we have demonstrated for the first time that the yeast mitogen-activated protein (MAP) kinase Hog1 is essential for the cells in response to KP1019. Hog1 is rapidly phosphorylated upon treatment with KP1019, and the deletion of the HOG1 gene potentiates the growth inhibition effect of KP1019. Moreover, we also observed the up-regulation of glycerol-3-phosphate dehydrogenase 1 (GPD1) mRNA in response to KP1019 treatment, a factor that is essential for the hyperosmotic stress response. Our results also reveal that membrane-bound sensor proteins of high osmolarity glycerol (HOG) pathway are crucial for Hog1 phosphorylation in response to KP1019-induced stress. Furthermore, KP1019 has also been found to increase the accumulation of ubiquitinated proteins and deletion of several members of ubiquitination pathways conferred sensitivity for KP1019. The findings presented here strongly suggest the ability of KP1019 to activate Hog1 MAP kinase and induce protein ubiquitination, which may underlie the therapeutic potential of this compound. In summary, we have disclosed a novel mechanism of KP1019 activity.